This invention relates to a textile material and, in particular, to a surgical mesh of knit construction fabricated from a polypropylene monofilament yarn.
Hernia repairs are among the more common surgical operations which may employ mesh fabric prosthesis. Such mesh fabric prostheses are also used in other surgical procedures including the repair of anatomical defects of the abdominal wall, diaphragm, and chest wall, correction of defects in the genitourinary system, and repair of traumatically damaged organs such as the spleen, liver or kidney.
Mesh fabrics for use in connection with hernia repairs are disclosed in U.S. Pat. Nos. 5,292,328, 4,769,038 and 2,671,444. Knitted and woven fabrics constructed from a variety of synthetic fibers and the use of the fabrics, in surgical repair are also discussed in U.S. Pat. Nos. 3,054,406; 3,124,136; 4,193,137; 4,347,847; 4,452,245; 4,520,821; 4,633,873; 4,652,264; 4,655,221; 4,838,884;. 5,002,551; and European Patent Application No. 334,046.
The examples of mesh that have been cited are focused on overcoming basic procedural needs regardless of foreign body effects on the patient. One example is Marlex mesh, which is a very dense knitted fabric structure with low porosity. The mesh, when utilized in some types of herniaplasty such as giant prosthetic reinforcement of the visceral sac (GPRVS), is considered too stiff and lacks the ability to conform to the natural shape of the patients anatomy. Further, the mass of polypropylene fiber per unit area is excessive relative to the strength provided by the reinforcement mesh.
The mesh disclosed in U.S. Pat. No. 5,292,328 (Hain et al.) is intended to be supple enough for GPRVS procedures and is manufactured out of a fine denier multi-filament polypropylene that has been stiffened. While the mesh is stronger than its multi-filament polyester procedural alternative, it relies upon a multi-filament construction and is stiffer than the polyester counterpart. Additionally, the use of a multi-filament textile in the presence of an infection is not desirable. It is generally believed that the small interstices between the fine filaments are able to harbor an infection and prevent proper healing of the wound. Further, the increase surface area due to the fine denier filaments causes the mesh structure to become extremely opaque or reflective to endoscopic camera lighting.
With the advent of endoscopic hernia repair, a need to produce meshes that are less reflective of the high intensity lighting, utilized to perform the surgery, and enables visualization of repair sight through the mesh itself is necessary. U.S. Pat. No. 5,569,273 (Titone) discloses a dual bar warp knitted structure that attempts to increase the pore size of the mesh and reduce the reflective surfaces of the knitted structure. While this construction increases the pore size of the mesh, it degrades the strength of the knitted structure. Further, the knitted structure results in a fabric that is too stiff for GPRVS procedures and increases total fabric density. Additionally, the open individual cells do not enable fixation near the edge of the knitted mesh structure after cutting.
In all of the examples cited, the meshes are provided, and intended, as the long-term primary structural support for the abdominal wall repair. From a patient need perspective, the growth of scar tissue on the mesh provides a large portion of the final structural integrity of the implanted prosthesis. The mesh is simply a scaffold upon which the scar tissue may form. This is apparent given the fact that as the natural scar tissue contracts during healing, the mesh effectively becomes embedded within the scar itself and is no longer flat and is therefore unable to exert tensile reactive forces. Therefore, the initial mesh burst strength is only relevant prior to scar tissue formation and does not need to exceed the forces capable of being held by the points of fixation. In the presence of the scar tissue, all of the examples cited are excessive relative to the clinical need of the patient and simply add to the mass of foreign matter residing in the body after natural healing has occurred
It is desirable for surgical mesh fabric prosthesis to exhibit certain properties and characteristics. In particular, the mesh should have a burst strength sufficient to ensure that the mesh does not break or tear after insertion into a patient. The mesh should also have a pore size that enables easy visualization of structures through the mesh, minimize camera light reflection and provide a density of crossing fibers sufficient to facilitate fastening in an endoscopic environment. In addition, the construction of the mesh should provide the maximum burst resistance while minimizing foreign body mass and enhancing fabric pliability.
It is an object of the present invention to provide a knitted surgical mesh having a high burst strength/fabric weight ratio, possessing a large pore size (with a density of crossing fibers to enable easy fastening), which has a greater flexibility than known knitted surgical mesh fabrics while minimizing foreign body mass in the clinical environment.
These and other objects and advantages of the invention will become more fully apparent from the description and claims, which follow or may be learned by the practice of the invention.
The present invention is directed to a knitted surgical mesh formed from a yarn. The knitted mesh has from 40 to 80 courses per inch and from 7 to 11 wales per inch, a flexibility of from about 80 to about 250 mg-cm, a burst strength greater than 105 pounds per square inch and an average porosity of greater than 50%.